This application relates generally to fireproofing products and more specifically to fireproofing panels.
Fireproofing is an important segment of an overall fire protection system to protect people and property. The fireproofing is applied over some type of substrate. Typically, fireproofing is applied to structural members in areas where a fire can occur. In the event of fire, fireproofing will retard the rate of temperature increase in the structural members such that the failure temperature of the members can be delayed for as much as several hours. During the period of delay, the fire may be extinguished or, at the least, the structure can be safely evacuated. When no fireproofing is used, structural members have been known to fail, thus resulting in structure collapse, in less than 15 minutes.
Fireproofing is also applied to elements such as walls, bulkheads, or decks. In a fire, the fireproofing delays an increase in temperature behind the element. Where flammable material is stored behind the element, the fireproofing can prevent ignition of the material, hopefully until the fire is extinguished.
Fireproofing is also applied to pressure vessels. The fireproofing reduces the possibility that the vessel will rupture. Thus, the fireproofing reduces the chance of explosion or release of hazardous material from the vessel.
Fireproofing is also used over cable trays. The fireproofing can keep the circuitry in the tray functioning for an extended period of time in the event of a fire.
One widely used type of fireproofing is a char-forming coating. The coating can be called ablative, subliming, or intumescent. As supplied, these coatings can be in the form of a low viscosity paint or a high viscosity mastic. These coatings are sprayed or troweled or brushed on to a substrate.
Some of these coatings are used in combination with a mesh element. Some coatings utilize a flammable mesh, others a non-flammable mesh such as one fabricated from steel. With some coatings, the mesh is mechanically mounted on the substrated; with others, it is simply embedded in the coating.
When these coatings are exposed to a fire, they undergo a number of changes of state--solid to liquid, liquid to gas, and solid to gas--absorbing some of the energy of the fire, and insulating the substrate. Fire exposure results in the formation of a char which, depending on the material, can be thicker, as thick, or less thick than the thickness of the non-fire exposed coating.
The above-mentioned mesh element may perform one or more functions. Mesh might be used to retain char on the substrate. It might be used to retain the fireproofing material on the substrate before a fire even if the fireproofing material adheres to the substrate. In other instances, the mesh reinforces the fireproofing prior to a fire to reduce damage to the coating of fireproofing which could be caused by impact or movement of the substrate.
One example of a fireproofing compound which forms a char is CHARTEK intumescent epoxy coating sold by Textron Specialty Materials of Lowell, Mass., USA. Other such materials are described in U.S. Pat. No. 3,849,178, issued to Feldman.
It has been suggested that the cost of installing fireproofing could be reduced if the substrate were covered with fireproofing panels. Panels could be installed without the special equipment needed to apply coatings of fireproofing material. Also, surface preparation needed before a coating can be applied could be eliminated if panels were used. Further, a coating can be applied to an outside structure only if weather conditions are favorable while the coating is applied and is curing. Installation of panels is much less dependent on weather conditions.
Panels made of fireproofing material similar to concrete are commercially available. For example, U.S. Pat. No. 4,567,705, to Carlson describes such panels. To protect a substrate, steel studs are welded to the substrate in a predetermined pattern. The stud positions match holes in the panels. The panels are then mounted on the studs and bolted to the substrate.
To cover a substrate larger than a single panel, many panels are mounted to the substrate. The panels are butted together. The space between the panels is caulked to provide a barrier to moisture. The panels are, however, very heavy and are difficult to install in some places. Also, such panels are not used where the fireproofing must have an A or a H rating.
Lightweight pieces made from char forming compounds have also been suggested. U.S. Pat. No. 4,493,945, shows lightweight pieces of fireproofing material used to cover a substrate. Relatively complicated fastening mechanisms are employed. Morever, it is necessary to still use char-forming compound in its liquid (mastic) form to seal the seams between pieces.
The pieces shown in U.S. Pat. No. 4,493,945, have also been formed as panels. The panels are attached to walls or large substrates by bolting them to studs mounted to the substrate. The joints between panels and the bolts are then covered by a char-forming compound in liquid form.
Such a system could be improved in several ways. First, the need to seal seams with fireproofing material requires favorable weather conditions, which is one of the disadvantages of the sprayed-on and troweled-on mastics. Also, metal studs conduct heat to the substrate. If adequate precautions are not taken, the studs might conduct enough heat to the substrate during a fire to damage the substrate. Even where no damage to the substrate occurs, the studs may conduct enough heat to make hot spots on the substrate. These hot spots prevent the fireproofing system from qualifying for an A or H fire rating. Also, the panels must be carefully installed to keep the joints between panels very small. Even with careful installation, the seams represent weak points in the fire protection which may fail in an explosion or if exposed to a burning gas jet. Such causes of stress on the joints are likely to occur during a fire. Even with no particular stress, the joints between panels may open as the fireproofing material of the panels undergoes state changes in a fire.